Projectile trapping method and apparatus



Aug. 29, 1944. 1. R. GILSON PROJECTILE TRAPl ING METHOD AND APPARATUS Filed July 28, 1943 2 Sheets-Sheet 1 INVENTGR v IRVING R. GlLsnn B Z Z f:

A'r'rnRnEY Aug. 29, 1944. 1. R. GILSON v PROJECTILE TR A PPING METHOD AND APPARATUS- Filed July 28, 1943 -2 Sheets-Sheet 2 INVENLTDR IRVING 121311.501!

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ATTEIRNEY Patented Aug. 29, 1944 PROJECTILE TRAPPING METHOD AND APPARATUS Irving R. Gilson, Liverpool, N. Y., assignor of onefltth to Theodore E. Simonton, Syracuse, N. Y.

Application July 28, 1943, Serial No. 496,522

11 Claims.

This invention relates to projectile trapping, and relates more particularly to the trapping of projectiles projected at high velocity substantially along a preselected trajectory, as in the testing of firearms during manufacture by actual firing.

For such test firing of firearms, it has been customary to employ a sand trap in which the bullets are caught and stopped in a pile of sand. Such sand traps have numerous, well-recognized objections. The bullets accumulate in the sand, forming masses of metal apt to cause a later bullet to ricochet, and hence the bullets must be sifted out of the sand frequently. This is a messy and unpleasant operation and is even dangerous to the health of the workmen, as the successive impacts of the bullets pulverize the sand tion, such as an open field or a factory roof-top,.

as the flour produced floats in the air and is very abrasive, as well as dangerous to health. The used sand is simply a waste product, and must be carted away to a dump. The bullets recovered from the sand are so impregnated with particles of sand that the metal has little, if any, value as scrap metal. Moreover, the original installation of a sand trap is fairly expensive, due principally to the construction features required for safety and to keep the sand dry in an out-of-doors location.

According to my invention, all of the above difiiculties are overcome. The bullets are projected into a comparatively slowly flowing, compressible stream of mixed liquid and gas confined in and substantially filling a pipe of moderate diameter and length. The compressible flowing stream absorbs the impact of the bullets and reduces their velocity to substantially that of the flowing stream, whereupon the stream and the bullets are discharged into a reservoir from which the liquid may be pumped for re-use and from which the collected bullets may be removed periodically in a clean condition in which they command a good price as scrap metal. safe and eliminates all dangerous ricocheting; is entirely clean and hence ofiers no threat to health or to nearby machinery; is more convenient to use than a sand trap; costs somewhat less My trap is Figure 2;

Figure 4 is a, detail planview taken on the line 4-4 of Figure 1; and

Figure 5 is a detail section taken on the line 5-5 of Figure 1.

Referring more particularly to the drawings, my bullet trap comprisesa target tube [0 conveniently formed of three pipe sections secured together by customary flanges and bolts, constituting respectively the nozzle section II, the shock-section l2 and the tail section l3. These sections may be made of appropriate lengths of standard 4" pipe, the nozzle section II being conveniently made of a 33" length flanged at only one end, the shock section I! of a 37" length of extra heavy wall thickness flanged at both ends, and the tail section iii of a 10' length flanged at only one end.

The nozzle section H is provided with a plurality of nozzles l4, conveniently four in number, the construction and arrangement of which are shown in detail in Figures 2 and 3. As there illustrated, each nozzle [4 comprises an outer casing l5 consisting of a piece of 2" pipe welded into a suitable aperture IS in the wall of the nozzle section II so that the axis of the casing l5 forms an acute angle of preferably seventeen to twenty degrees with the axis of the nozzle section II. Within the casing I5 is located a 1%" nozzle tube l6 provided near its inner end with a guide ring ll secured thereto and at its outer end with a 1 pipe coupling I8 threaded r thereon. The inner end IQ of the tube I6 is preferably out 01f square, reamed smooth and slightly flattened as shown, so as to deliver a smooth, solid stream of water. Before assembly, both the guide ring l1 and the coupling I 8 are machined to form a press fit inside the casing l 5. The tube IS, the guide ring I! and the coupling l8 may then be pressed into the casing l5 as a unit. The inner end I 9 is preferably solocated as barely to project at one side into the opening I5, as illustrated in Figure 3.

The four nozzles 14 are preferably equally spaced around the circumference of the nozzle section II to form two diametrically opposed pairs of nozzles, and the nozzles of one pair are preferably located two inches in advance of the nozzles of the other pair, as best shown in Figure 3.

To the couplings l8 are connected, by suitable connections such as 1%" unions 20, lengths of flexibl 1 hose 2|, the other ends of which are joined by 1%" unions 22 to a 3" manifold 23, best shown in Figure 4. The 3" pipe 24 supplies water for the nozzles to the manifold 23. The pipe. 24 is connected with the outlet of a pump 25 driven by a prime mover such as an electric motor 26, and is preferably provided with a pressure regulating valve 21 and a pressure gauge 28. The pump 25 may have a capacity of 150 gallons per minute at a 30 foot head.

The outlet end of the tail section I3 is threaded into a 4" coupling 30 welded in an end wall of a steel tank 3|. The tank 3| may conveniently be 8' long, 4' wide and 3'6" high. The tank 3| is strongly made of heavy steel and, as a precaution against accidents, is provided with an inverted trough 32 made of 1%" armor plate, located over the inner end of the coupling 30 and inclined downward into the tank. The inner end of the trough 32 may be supported by a hook 33 hung on a rod 34 extending across the top of the tank. As a further safety measure, a bafile plate 35, likewise of 1 armor plate, is located at the rear of the tank 3|, the baffle plate 35 being substantially coextensive with the rear wall of the tank 3| and preferably inclined as illustrated. The tank 3| is also provided with a drain 33 controlled by a suitable shut-oil valve. A pipe 31 is connected to the tank 3| near its bottom and to the inlet of the pump 25. The tank 3| is also provided with an overflow pipe 38 leading to a suitable sewer.

The nozzle section II is provided at its bottom near its inlet end with a drain aperture 40, to which is connected a return pipe 4| discharging into th tank 3|.

The outlet end of the tube I is supported by the coupling 30 and the tank 3| as described above, and further support for the tube l0 may be provided by the post 45. As shown in Figure 1, the post 45 may also support the overflow pipe 33 and the return pipe 4|. A standard 46, conveniently made of pipe fittings, may be used to support the manifold 23 and its associated parts.

The bullet trap above described is preferably located in a separate room to which access may be obtained only through a suitably locked door, and several such traps may conveniently be installed side by side in the same room. Warning signals are preferably provided telling the testing operators not to flre while the door of the trap room is unlocked.

The wall of the trap room opposite the inlet end of the trap is indicated in Figure 1 at 50. .An

aperture 5| is provided in this wall through which may be inserted the barrel 52 of the machine gun 53 or other firearm to be tested, suitable clearance for recoil of the gun being provided by the aperture 5| as indicated in Figure 1. The machine gun 53 is securely fastened for test firing to a fixed stand 54 diagrammatically illustrated in Figure 1, the stand 54 being so located that when the firearm to be tested is secured thereto, its muzzle will project through the aperture 5| in alignment with the axis of the tube I0, so that the trajectory of the bullet, which is nearly flat near its origin, will substantially coincide with the axis of the tube "I.

As illustrated in Figure 1, the muzzle of the barrel 52 is preferably spaced a few feet from the inlet end of the tube During operation of the trap, this space is preferably deluged with water from water sprays, not illustrated, for the purpose of laying any unburned powder issuing from the gun muzzle. This water, carrying the powder, is permitted to run off to waste through sewer connections, not illustrated, in the floor of the trap room.

In operation, the tank is filled with water to approximately the level of the overflow pipe 33, and to this water there is preferably added a socalled soluble oil, such as is used as a cutting oil for lubricating metal parts to be machined, in the proportions of one gallon of soluble oil to 400 gallons of water. The pump 25 is then started, and the pressure valve so regulated that the pressure gauge 23 shows a pressure of, for the pipe sizes above described, in the neighborhood of 4% pounds per square inch gauge pressure. This pressure is less than that necessary to produce solid liquid flow in the tube l0, and it will be observed from the dimensions given above that the cross-sectional area of the four nozzle tubes I6 is less than that of the tube Ill. As a result of these conditions and of the angular arrangement of the nozzles l4, air is aspirated through the inlet end of the nozzle section I I and a stream of commingled water and air flows through the tube l0 toward the coupling 30, discharging into th tank 3|. This stream substantially fills the shock section I2 and the tail section 13 of the target tube I0, but very little water flows back toward the inlet end of the nozzle section I, and what little does is drained into the tank 3| through the return pipe 4|.

The stream of mixed water and air thus created in the tube In flows in the same general direction as the bullet trajectory and is compressible, and is thus enabled to take the impact of a series of bullets fired in rapid succession from the machine gun 53 or the like. A bullet trap as described above has been successfully used with both .30 caliber and .50 caliber machine gun bullets. The .50 caliber bullets have an impact force in the neighborhood of five tons. The compressible flowing stream of air and water cushions this impact and absorbs its force by compression of the air bubbles. It is possible that a rise in pressure in the tube l0 caused by the impact of the bullet creates a condition similar to that in the eduction pipe of an air-lift pump, in which the water and the air, as is well known, form alternate layers or pistons. This, however, is purely speculative, and has not been checked.

The shock caused by the impact of the bullets largely occurs in the few feet of the tube I0 immediately beyond the nozzle assembly. It is for this reason that this section I: of the tube In is called the shock section and is made of extra heavy pipe. There is a tendency for the bullets to be deflected by the stream of water and air and to strike against the wall of the shock section. This result is evidenced by the deformed shape of the bullets recovered from the tank 3| and also by marks on the inside of the shock section. Such marks do not appear in the tail section, indicating that the bullets lose most of their kinetic energy during their passage through the shock section. With .30 caliber ball ammunition, the marks are very slight, and a shock section of ordinary extra heavy cast iron 4" pipe mediately beyond the other, forming in efiect' is amply strong to stand the strain and will last indefinitely. With .50 caliber ball ammunition, the marks are definitely heavier, and the striking of the bullets against the inside of the shock section is apt to cause such a pipe to split after perhaps a. number of weeks of daily service. The split is usually a single thin crack several inches long, and does not prevent the functioning of the trap, doing no harm aside from a leakage of water. It is desirable, however, to shut down the trap before thesplit becomes larger, and insert a new shock section. Due to the construction of the trap, this is a simple operation requiring only a few minutes.

With .50 caliber armor piercing ammunition, the marks above referred to became long gouges in the inside of the shock section, and greatly decrease its life. The use of the trap is therefore not recommended with such ammunition, although it is possible to operate with it, and such bullets have been satisfactorily trapped as above described. gouging problem could be overcome by using a chilled steel shock section. -Fortunately, however, it is not ordinarily necessary to test machine guns in the factory with armor piercing ammunition.

In the first trap constructed in accordance with my invention, four nozzles were used equally spaced circumferentially around the nozzle section I and at the same distance from the end of the nozzle section, and the ends I 9 of the nozzle tubes 16 were round. The result was to create a turbulent mixture of air and water at the point where the resultant nozzle streams converged, which is likewise substantially the point at which the bullets were intercepted by the flowing stream. Due to this turbulent condition at the interception point, considerable deflection of the bullets wasexperienced, and the bullets collected in the tank 3| were quite severely deformed, principally by having their forward ends bent over. By the nozzle assembly described in detail above, in which the nozzle tubes are flattened and arranged in pairs spaced apart longitudinally of the nozzle section, two converging V- shaped streams of water are obtained, one imtwo adjacent V's arranged at right angles to one another. As a result of this nozzle construction, the bullet tends to be centered by the converging streams of water at the interception point, and hence there is less tendency for the bullets to be deflected toward the wall of the shock section. This has been demonstrated in practice by the diminution of the marks on the inside of the shock tube and the lessened deformation of the bullets after the foregoing change in the nozzle assembly was made.

My trap has not as yet been used with projectiles larger than .50 caliber. There seems to be no reason, however, why it could not be used to test larger sizes of firearms, but in the case of a decided increase in the diameter of the projectile, it would bedesirable to use a larger size pipe for the target tube I and to increase the nozzle sizes and the water pressure accordingly. This is for the reason that there is bound to be some deflection of the projectiles, and suflicient space should be provided between the interception point and the wall of the shock tube so that a projectile will be substantially decelerated before it strikes the wall of the shock tube.

The manner in which the bullets are deposited in the tank 3| strongly suggests that they issue It seems probable that the from the tail section B at approximately the velocity of the flowing stream. It will be readily apparent that the velocity of the flowing stream is only an exceedingly small fraction of the muzzle velocity of a .50 caliber machine gun bullet, for example, and that, therefore, the bullets have lost all or nearly all of their kinetic energy in the flowing stream before they are deposited in the tank 3|.

In order to clean the bullets out of the tank 3| it is only necessary to drain the tank through the drain 36 and shovel the bullets out of the tank. Even where the trap is in use substantially continuously for the entire working day, it will sufllce to do this only at the close orthe day. As many as 20,000 rounds of ammunition may be fired before it is necessary to clean out the tank, whereas with the ordinary sand trap, cleaning is usually necessary at the end of each 5,000 rounds.

Although I have described my invention, in accordance with the patent statutes, specifically and in detail and in the best form now known to me, it will be appreciated that many changes and modifications may be made by those skilled in the art without departing from the spirit of my invention. I desire, therefore, to be limited only by the prior art and the scope of the appended claims.

I claim:

1. The method of decelerating a projectile traveling at high velocity substantially along a preselected trajectory, which comprises intercepting the projectile at a selected interception point near the origin of said trajectory in a compressible commingled stream of liquid and gas flowing in the general direction of said trajectory at a very slow speed compared to the initial velocity of said projectile, and confining said compressible flowing stream and the projectile laterally in all directions against departure from a limited zone surrounding said trajectory from said intercep- .ously bringing liquid angularly into said trajectory inthe general direction of said trajectory at a selected projectile interception point near the origin of said trajectory, commingling said liquid with gas at said interception point to form a compressible'mixture, confining the compres-- sible mixture in a stream, causing said stream to flow in said general direction at a very slow speed compared to the initial velocity of the projectile, said confining being such that the compressible flowing stream and the projectile are confined laterally in all directions against departure from a limited zone surrounding said trajectory, continuing said confining from said interception point to a point where the initial velocity of the projectile has been reduced substantially to the velocity of said flowing stream, and thereafter discharging said stream and the projectile from the confined zone.

3. In the art of testing fire arms by actual firing resulting in the projection of a bullet at high velocity substantially along a preselected trajectory, the method of trapping such a projected bullet which comprises causing said trajcctory to coincide for a small portion of its normal length near its origin with a laterally confined stream of mixed liquid and gas flowing in the general direction of said trajectory at a very slow speed compared to the muzzle velocity of the bullet, whereby at least the major part velocity of the bullets, whereby at least the major part of the kinetic energy 01' the bullets is absorbed in said flowing stream, and discharging said flowing stream and bullets when moving at substantially the speed of said stream into a reservoir.

5. The method of decelerating a projectile which comprises providing a substantially straight length of pipe having an inlet end open to the atmosphere and an outlet end, producing and introducing near the inlet end of the pipe a stream of mixed liquid and gas substantially filling said pipe and flowing continuously toward and out of the outlet end of the pipe, projecting a projectile to be trapped through the atmosphere into the inlet end of said pipe in the general direction of the length or said pipe at an initial velocity greatly exceeding that of said flowing stream, and absorbing at least the major part of the kinetic energy of said projectile in said flowing stream of liquid and gas, whereby the projectile emerges from the outlet end 01' said pipe at a velocity not greatly difl'erent from that of said stream.

6. The method of decelerating a projectile which comprises providing a substantially straight length of pipe having an inlet end open to the atmosphere and an outlet end, introducing liquid into said pipe adjacent said inlet end in such manner as to aspirate gas from the atmosphere and to produce a stream of mixed liquid and gas substantially filling said pipe and flowing continuously toward and out of the outlet end of the pipe, projecting a projectile to be trapped through the atmosphere into the inlet end of said pipe in the general direction of the length of said pipe at an initial velocity greatly exceeding that of said flowing stream, and absorbing at least the major part 01' the kinetic energy of said projectile in said flowing stream of liquid and gas, whereby the projectile emerges from the outlet end of said pipe at a velocity not greatly different from that of said stream,

7. A projectile trap for receiving and decelerating 'a projectile traveling at high velocity substantially along a preselected trajectory, comprising in combination, a length of pipe having an inlet end open to the atmosphere and an outlet end and having an internal diameter considerably greater than the diameter of said projectile and arranged so that its axis substantially coincides with said preselected trajectory, and means for producing a stream of mixed liquid and gas substantially filling said pipe and flowing continuously toward and out of said outlet end of the pipe at a speed greatly less than the initial velocity of the projectile to be trapped, whereby a projectile projected at high velocity through the atmosphere into said inlet end of the pipe along said trajectory will have at least assaooa the major part oi. its kinetic energy absorbed in said flowing stream.

8. A projectile trap for receiving and decelerating a projectile traveling at high velocity substantially along a preselected trajectory, comprising in combination. a length of pipe having an inlet end open to the atmosphere and an outlet end and having an internal diameter considerably greater than the diameter of said projectile and arranged so that its axis substantially coincides with said preselected trajectory, and means for introducing liquid into said pipe adjacent said inlet end so constructed and arranged as to aspirate gas from the atmosphere and to produce a stream of mixed liquid and gas substantially filling said pipe and flowing continuously toward and out or said outlet end of the pipe at a speed greatly less than the initial velocity of the projectile to be trapped, whereby a projectile projected at high velocity through the atmosphere into said inlet end of the pipe along said trajectory will have at least the major part of its kinetic energy absorbed in said flowing stream.

9. A projectile trap for receiving and decelerating a projectile traveling at high velocity substantially along a preselected trajectory, comprising in combination, a length of pipe having an inlet end open to the atmosphere and an outlet end and having an internal diameter considerably greater than the diameter of said projectile and arranged so that its axis substantially coincides with said preselected trajectory, means for introducing liquid into said pipe adjacent said inlet endso constructed and arranged as to aspirate gas from the atmosphere and to produce a stream of mixed liquid and gas substantially filling said pipe and flowing continuously toward and out of said outlet end of the pipe at a speed greatly less than the initial velocity of the projectile to be trapped, said mean comprising nozzles leading into said pipe adjacent said inlet end at circumferentially spaced points and at acute angles to the axis of said pipe, the combined cross-sectional area of said nozzles being less than the cross-sectional area of said pipe, and means for supplying liquid to said nozzles at a pressure less than that required for solid liquid flow in said pipe, whereby a projectile projected at high velocity through the atmosphere into said inlet end of the pipe along said trajectory will haveat least the major part of its kinetic energy absorbed in said flowing stream.

10. A projectile trap for receiving and decelcrating a projectile traveling at high velocity substantially along a preselected trajectory, comprising in combination, a length of pipe having an. inlet end open to the atmosphere and an outlet end and havin an internal diameter considerably greater than the diameter of said projectile and arranged so that its axis substantially coincides with said preselected trajectory, means for introducing liquid into said pipe adjacent said inlet end so constructed and arranged as to aspirate gas from the atmosphere and to produce a stream of mixed liquid and gas substantially filling said pipe and flowing continuously toward and out of said outlet end of the pipe at a speed greatly less than the initial velocity of the projectile to be trapped, said means comprising a pair of opposed nozzles leading into said pipe adjacent said inlet end and at acute angles to the axis of said pipe, a second pair of opposed nozzles leading into said pipe at points spaced both longitudinally and circumferentially from said first pair of nomles and at acute angles to the axis of said pipe, the combined crosssectional area of said nozzles being less than the cross-sectional area of said pipe, and means for supplying liquid to said males at a pressure less than that, required for solid liquid flow in said pipe, whereby a projectile projected at high velocity through the atmosphere into said inlet end of the pipe along said trajectory will have at least the major part of its kineticenergy absorbed in said flowing stream.

11. A projectile trap for receiving and decelerating a projectile traveling at high velocity substantially alon a preselected trajectory, comprising in combination, a length of pipe having an inlet end open to the atmosphere and an outlet end and having an internal diameter considerably greater than the diameter of said projectile and arranged so that its axis substantially coincides with said preselected trajectory, means for introducing liquid into said pipe adjacent said inlet end so constructed and arranged as to aspirate gas from the atmosphere and to produce a stream of mixed liquid and gas substantially filling said pipe and flowing continuously toward and out of said outlet end of the pipe at a speed greatly less than the initial velocity of the projectile to be trapped, said means comprising nozzles leadin into said pipe adjacent said inlet end at circumferentially spaced points and at acute angles to the axis of said pipe, the combined cross-sectional area of said nozzles being less than the cross-sectional areaof said pipe, and means for supplying liquid to said nozzles at a pressure less than that required for solid liquid flow in said pipe, and a reservoir into which said outlet end of said pipe discharges, said reservoir constituting a source of liquid for said liquid supplying means, whereby said liquid may be re-used and whereby a projectile projected at high velocity through the atmosphere into said inlet end of the pipe along said trajectory will have its velocity reduced substantially to the velocity of said flowing stream and will be discharged into said reservoir.

IRVING R. GIBSON. 

